Recent studies have found that poor oral hygiene may foster the colonization of the oropharynx by potential respiratory pathogens in mechanically-ventilated (MV), intensive care unit (ICU) patients. Thus, improvements in oral hygiene in MV-ICU patients may prevent ventilator-associated pneumonia (VAP). The Specific Aims of this revised application are: 1) to organize the necessary infrastructure to develop and perform a pilot clinical trial to evaluate alternative oral hygiene procedures to prevent VAP; 2) to use this organization to perform a pilot clinical trial to determine if the use of oral topical chlorhexidine gluconate (CHX) will prevent dental plaque, oropharyngeal colonization by respiratory pathogens, and VAP in MV-ICU patients. This pilot longitudinal, double blind intervention study will consider the appropriate frequency of delivery of CHX to improve oral hygiene in MV-ICU patients. Preliminary data from these pilot studies will also allow accurate sample size calculations to be made for a large scale multi-center clinical trial; and 3) to perform molecular epidemiological studies to genetically type bacterial strains cultured from lower airway secretions of MV-ICU patients with or without VAP and compare them to strains of the same species isolated from their dental plaque. This pilot study will enable this multidisciplinary team of investigators to organize the infrastructure, patient recruitment and methodologic protocols, and data management and analysis procedures necessary to perform a multi-center, controlled clinical trial to assess the efficacy and generalizability of this intervention to improve oral hygiene in MV-ICU and prevent VAP.